It wasn't that many years ago that the tarp shelter was your only practical choice for ultralight travel. The "lightweight" tents on the market were generally over 5lbs (though Bibler was always there with their fine single-wall offerings - if you could afford the princely ransom to acquire one of the beauties).
Happily the past several years have brought forth some genuine options for ultralight shelters. No longer is the tarp shelter the true hallmark of the minimalist (though it still remains the lightest and my favorite for solo travel). These days we're treated to the option of full solo tents that weigh in at just over 2lbs, as well as 2-person options at just over 3lbs.
These days my favorite "bang for the buck" shelter is the Mountain Hardwear Lightpath 3. It's rated as a 3-season 3-person tent, but think of it as a luxurious, well designed tent that qualifies as a "2-person plus gear with a usable layout that you won't feel trapped inside". All for 5lbs 8ozs (2.5 kg) average packed weight, which is of course a pound or two heavier than other tents listed below, but when sharing the load with a partner it's a reasonable 2.75lbs per person. Add in a compelling price (as of Jan 2011 on sale for US$150) and it's worth a look. It's not freestanding, which I happen to prefer, and the usable length and volume make it a worthy replacment for my venerable (and discontinued) Sierra Designs Clip3 CD. Yes, as always I paid for it myself. I have no connection to any of the suppliers I mention.
The items listed here are on my short list - items I'd be happy to use (or have used) myself. I've used the tarp shelter, Waypoint, and Lightsabre. I've shared the trail with Tod and his Sierra Designs Light Year CD and he's always been happy with it. The Lighthouse is the only one I have no direct experience with, but the reviews have been so good that I feel it's worthy of inclusion. Plus all of this is just meant to give you some ideas - the list is by no means exhaustive. As always your mileage may vary.
Note that I don't include weight of guy lines, stakes, or Tyvek since in general all shelters listed below will use roughly the same amount of each (several ounces/grams give or take).
|Mountain Hardwear Lightpath 3||$150 (on sale)||5.5lbs / 2.5kg||My current favorite and workhorse tent when not traveling solo. Spacious and comfortable for 2 tall travelers. Excellent design, layout and volume for the weight. Not freestanding.||@#%&%$! It might be discontinued as of 2011! Why must all my favorite tents go extinct?|
|Tarp Shelter (A16 Bug Bivy + 8'x 10' Ultralight Backpacking Tarp)||$100 ($35+$65)||1.25lbs / 0.57kg total||Lightest option; Least expensive option; Versatile (various pitching techniques), can be airy or buttoned down, can pitch on awkward terrain.||Requires some skill to make truly weatherproof, some don't like the "open" feeling that tarp shelters generally have (pitching skills make a difference here).|
|Black Diamond Lightsabre Bivy (Bibler-inspired)||$185||1.4lbs / 0.62kg after seam sealing||Compact, weatherproof, very small profile, able to fit nearly anywhere your body can, light color and netting help allay claustrophobia.||Confining (getting dressed in a bivy is an art), possibly claustrophobic in long storm, tall people (6'+) need not apply.|
|Mountain Hardwear Waypoint 1||$195||2.2lbs / 1.0kg||Lightest tent in the list, room to get dressed, sit up a bit, etc. Amazingly light for a full-fledged tent.||No netting (you're buttoned down or you're wide open). Prone to condensation.|
|Mountain Hardwear Waypoint 2||$250 (2004 model $170 on sale)||3.1lbs / 1.4kg||Full 2-person tent, largest floor space (32.5 sq ft); room to get dressed, sit up a bit, etc.||A bit expensive, no netting (you're buttoned down or you're wide open). Prone to condensation.|
|Black Diamond Lighthouse Tent (Bibler-inspired)||$370||3.2lbs / 1.5kg||Full 2-person tent, more headroom than the Waypoint 2 (but higher wind profile), a backcountry palace for one, or 1lb 11ozs each if sharing*; Netting for views/ventilation.||Freakin' EXPENSIVE!|
|Sierra Designs Light Year CD||$140||3.25lbs / 1.5kg||Full solo tent, fits up to 6'6" person, room to get dressed, sit up, etc. Plenty of netting for ventilation and views.||Heaviest shelter on list.|
* You can't really "share" the load of single-wall tent since it's all one item, but the other person can carry the poles, ground cloth, stakes, guy lines, and a little extra gear to effectively balance the load.